A good random synonym depends on which of two very different jobs you need: arbitrary, haphazard, unplanned and chance describe things that happen without a pattern, while odd and unexpected cover the newer slang use, as in "that was so random."
Random also has a strict meaning in math and research, where it means every item had an equal shot at being picked. Finding another word for random in that sense is harder, and only a handful of terms keep the meaning. Below, every meaning comes with a short word list, some real swaps, and notes on the words that only look interchangeable.
Swatch at a glance
Best swaps
arbitrary, haphazard, unplanned, chance, oddPart of speech
Adjective (randomly is the adverb)Most formal
indiscriminate, arbitrary, stochasticMost casual
out of nowhere, hit-or-miss, weirdAntonyms
planned, deliberate, systematicWatch out
Arbitrary suggests someone made a choice with no good reason. Do not use it for a fair lottery draw.Word forms covered
random, randomly, randomness, at random
Pick the sense first
Ask yourself what kind of random you mean. Is it chaos, fairness, surprise, a stranger, or a mixed bag? The table sorts the strongest choices.
| Meaning | Try | Sample sentence |
|---|---|---|
| No order or plan | haphazard, unplanned, aimless | The books sat in haphazard piles. |
| Choice with no reason | arbitrary, indiscriminate | The fines felt arbitrary to drivers. |
| Fair, by lot | randomized, chance | Each patient joined a randomized group. |
| Surprising (slang) | weird, odd, out of nowhere | He sent me an odd meme at 3 a.m. |
| Unknown person | unknown, unfamiliar | An unfamiliar man waved at us. |
| A mix of things | assorted, miscellaneous | A box of assorted cables. |
Random synonym choices, chatty to formal
That strip of chips moves from the way friends talk to the way a report reads. Out of nowhere is pure conversation. Hit-or-miss is relaxed and suggests mixed results. Haphazard sits in the middle and carries a hint of carelessness. Arbitrary belongs in essays and complaints about rules. Indiscriminate ranks as the most formal and tends to sound negative: indiscriminate cutting of trees, indiscriminate use of pesticides.
A handy test: if a person made the choice and you want to blame them, use arbitrary. If nobody chose at all, use chance or unplanned.
Random in real sentences, rewritten
- The teacher made random changes to the seating chart becomes the teacher made arbitrary changes.
- We met by random becomes we met by chance (the original is not correct English).
- His notes were in a random order becomes his notes were in a haphazard order.
- Some random guy called me becomes a stranger called me.
- A random sample of voters stays as it is in research, or becomes a randomly selected group of voters.
- That comment was so random becomes that comment came out of nowhere.
Text to a friend: "Random question, are you free Friday?" Swapping in quick question or out of the blue keeps the light tone, but random still works here and sounds natural in chat.
The research meaning needs care
In science, statistics and surveys, random is a technical term. A random sample gives every member of a group the same chance of selection, so you should not swap it for haphazard or arbitrary, which suggest sloppy work. Use randomized for trials and chance for outcomes ("the result could be due to chance"). Stochastic appears in advanced math and modeling; skip it in general writing. Our list of words for essays has more help with wording.
When random means weird or unexpected
Younger speakers often use random to mean strange, off-topic, or surprising. It is informal and fine in texts, but in a school paper choose a precise word. Unexpected stresses surprise, odd stresses that something does not fit, and bizarre is much stronger. Out of left field is an American idiom for an idea nobody saw coming. More options sit on the unexpected synonyms and strange synonyms pages.
Work email: "Sorry for the random message." A better version: "Sorry to write out of the blue." It sounds polite and does not make your note seem pointless.
Randomly and at random
For the adverb, try by chance, haphazardly, arbitrarily or indiscriminately, matched to the same senses as above. The phrase at random can become without a pattern or blindly (pick a card blindly). For the noun randomness, use unpredictability, chance or, in a negative light, disorder.
Opposites of random
The antonyms depend on the sense you started with. Against chance, use planned, deliberate or intentional. Against disorder, use systematic, methodical or ordered. Against a vague pick, use specific.
- The damage was deliberate, not random.
- She takes a methodical approach to filing.
More adjectives live under describing words.
Frequently asked questions
Which word can replace random most often?
Arbitrary, haphazard, unplanned and chance are the most useful. In slang, odd or unexpected replace the "that was random" use.
Is arbitrary the same as random?
Not quite. Arbitrary means a choice was made without a good reason, often by someone in charge. Random can mean pure chance with no chooser at all.
Which random synonym sounds formal?
Indiscriminate and arbitrary are the formal picks for everyday writing. In research, keep random or use randomized, since the meaning is technical.
How do I describe a random person more politely?
Say a stranger, someone I did not know, or an unfamiliar person. These sound kinder and clearer than some random guy.
What is the opposite of random?
Planned, deliberate, intentional and systematic are the main antonyms. Choose based on whether you mean purpose or order.
Can I use random in an essay?
Yes, in its strict meaning, such as a random sample. Avoid the slang sense in essays and replace it with unexpected, unrelated or odd.